Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Beyond annotations (readOnlyHint=false, idempotentHint=false, openWorldHint=false), the description discloses the URL's 15-minute validity, that the file is PUT directly to the returned URL, that a curl command and in-app destination page are also returned, the 25 MB cap, per-destination format whitelists, and that a vault file name must be free in its folder. What remains unsaid is permission/role requirements and whether any follow-up registration call is needed to finalize the upload.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Is the description appropriately sized, front-loaded, and free of redundancy?

It is front-loaded with the action and destinations, then return values, then hard constraints. The sentences are long and list-heavy, but each clause (validity window, size cap, format whitelist, name-free rule) carries operational information rather than filler.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

For a two-mode tool with a nested destination object and an output schema, the description covers modes, return payload, size/format limits and naming constraints. The main remaining gap is the end-to-end workflow: whether the PUT alone completes the upload or whether register_upload must be called afterwards, plus any authorization prerequisites.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema coverage is 100%, so the baseline is 3, but the description genuinely adds meaning: file_name uniqueness per folder, the 25 MB limit tied to content_length, allowed MIME types per destination kind, and that file contents cannot be passed as text. It stops short of giving a path syntax example beyond what the schema already shows.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Does the description clearly state what the tool does and how it differs from similar tools?

The description states a specific verb and resource ('Starts uploading one file to Lightbringer') and enumerates the two destination kinds with what each produces (a new drawing in an innovation's Illustrations section vs. a file in the vault). It is clear what the tool does, but it never distinguishes itself from the sibling register_upload or create_asset, which an agent must choose between.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Does the description explain when to use this tool, when not to, or what alternatives exist?

Usage is implied rather than stated: the description explains what each destination kind is for, which helps an agent pick the right destination object, but there is no explicit 'use this when' / 'use X instead' guidance and no mention of how this relates to the sibling upload/register tools.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.